Photographic apparatus

ABSTRACT

A photographic apparatus including an image intensifier for increasing writing speed and resolution for preferably recording light information displayed on a cathode ray tube is disclosed. The image intensifier intensifies the light image received at the input end thereof through optical lens and also converts the spectrum of the output light into a preferable range in which the photographic film is most sensitive.

United States Patent 1191 Stock et al.

1451 May 7,1974

PHOTOGRAPHIC APPARATUS [54] 3,608,452 9/1971 Conrad 95/12 [75] Inventors: W. Riley Stock; Melvin M. Balsiger, both of Portland; William G. Beran, 2:927:215 3 9 0 Beaverton, all of Oreg. 3,643,021 2/ 1972 Assignee: Tektronix Inc. Beaverton, Greg. 3,684,365 8/1972 Dahlqulst 346/110 [22] Filed: Sept 13 1971 FOREIGN PATENTS OR APPLICATIONS 4 8 64 G B" ..2502l3R [211 App o 5 967 43 I19 reat main Primary ExaminerArchie R. Borchelt [52] US. Cl. 250/213 R, 346/110 Assistant ExaminerD C, Nelms [5 1] Int. Cl. H01j 31/50 Attorney, Agent, or Firm-Adrian J. La, Rue [58] Field of Search 250/213 R, 213 VT, 65;

313/103; 95/12; 346/110, 74 CR ABSTRACT [56] References Cited A photographic apparatus including an image intensi- UNITED STATES TE T fier for increasing writing speed and resolution for 3,478,216 11/1969 Carruthers 250 213 v7 Preferably recordirfg light P F 9" a 3,050,623 8/1962 McNaney 250/213 R F q y H1062 1S d1sc1osed. The image 1ntens1fier 3,244,891 4/1966 Orthuber 250/213 R mtenslfies the llght Image fecelved at the Input end 3,633,478 1/1972 lShlmatSU 250/213 VT thereof through optical lens and also converts the 3,628,080 12/1972 Lindeqvist 250/213 VT spectrum of the output light into a preferable range in 3,184,753 5/1965 Koster 346/1 10 R which the photographic film is most sensitive, 2,890,923 6/1969 Huebner 346/74 3,235,658 2/ 1966 Levy 178/6] 7 Claims, 2 Drawing Figures (v g 1 33 18 2o 5 36 3 WENTEUHAY 11974 8808888 Fig-I ATTORNEY/I BACKGROUND OF THE INVENTION A photographic apparatus is frequently used to obtain permanent records of light images. However, the writing speed of a conventional photographic apparatus is limited by both of the lens and photographic film. Therefore, it is very difficult to obtain photographic records of dim objects or very fast images such as traces displayed on a cathode ray tube.

Various efforts have been made for increasing the writing speed of a photographic apparatus including prefogging technique, wherein a photographic film is exposed to a dim light over the entire surface thereof before being exposed to the image to be photographed. The prefogging can be achieved by bombarding the entire screen of the cathode ray tube with a flood electron beam for a short time or by applying flash current to a plurality of lamps positioned somewhere close to the photographic film. Although the above-mentioned prefogging techniques enhance the writing speed of the photographic film by a factor of ten or so, this is not effective enough.

The electronics field is devoted to utilize higher frequencies and faster signals. Naturally, this causes a need for measuring instruments such, for example, as an oscilloscope for displaying such high frequency signals. In the case of the occurrence of a single phenomenon, which is a high frequency transient signal and which is the case that photography is most useful and necessary, the trace intensity decreases substantially in direct proportion to the sweep speed because the number of electrons bombarding a given portion of the phosphor screen in a given time decreases according to the spot speed. This requires a photographic apparatus having a higher writing speed.

SUMMARY OF THE INVENTION According to the present invention, an image intensifier is provided between optical means and a photographic film. The optical means transmits an input light image to the input end of the image intensifier at a desired size. The image intensifier includes a photo cathode which generates a photoelectron beam corresponding to a well-focused light image transmitted thereto, for example, from the screen of a cathode ray tube. The photoelectron beam is accelerated and bombards a phosphor screen. Then the light emitted from the phosphor screen will be transmitted to the photographic film through a fiber optics member.

As the photocathode and the phosphor screen are close together and the potential gradient therebetween is very high and uniform, this image intensifier transmits a light image with negligible degradation, and the original light image can be intensified by a factor of 20 or more.

It is, therefore, one object of the present invention to provide an improved photographic apparatus which has increased writing speed and resolution.

It is another object of the present invention to provide an improved photographic apparatus which is simple and compact in construction, lightweight and economical.

It is still another object of the present invention to provide an improved photographic apparatus for recording traces displayed on a cathode ray tube.

The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference characters refer to like elements.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a simplified cross-sectional view of one embodiment of the present photographic apparatus employed for taking photographs of waveforms displayed on a screen of a cathode ray tube; and

FIG. 2 is an enlarged cross-sectional view of one embodiment of an image intensifier of FIG. 1.

DETAILED DESCRIPTION OF PREFERRED' EMBODIMENT Referring to the drawings, a photographic apparatus according to the present invention is described hereinafter in detail.

In FIG. 1, a cathode ray tube 10 is a conventional one having an evacuated envelope 12, a flat faceplate 14 of light transparent material, a phosphor screen 16 provided on the inner surface of the face plate 14, an electron gun 18 for producing electron beam 22 and deflection means 20 for deflecting electron beam 22 according to an input signal to be observed from a signal source 24. Of course, the cathode ray tube 10 may be a traveling wave type which is especially useful for high frequency display devices.

A light image of a waveform or information will be produced on the phosphor screen 16 of the cathode ray tube 10. The phosphor material for the phosphor screen 16 is normally P-31 because of its high luminance capability. The deflection means'20 is a conventional electrostatic or electromagnetic deflection device normally comprising a vertical deflection device connected to the input signal source and a horizontal deflection device connected to a sweep signal generator which generates a ramp signal representing time in synchronism with the occurrence of the input signal.

A photographic apparatus 26 of the present invention consists of a housing 28 sealed completely from external light, optical means 30, an image intensifier 32 and a photographic film holding device 34 which are provided in the housing 28 on the same axis. A side plate of the housing 28 facing the photographic film holding device 34 is suitably mounted on the main frame of the housing 28 by hinge means so that the photographic film in device 34 can be replaced. The optical means 30 includes at least one lens 36 for transmitting the light image formed on the screen 16 of the cathode ray tube 10 which may now be visually optimized to the image intensifier 32 at a desired image ratio, an iris 38 for adjusting the amount of light transmitted by the optical means 30 and a shutter 40 for controlling the passage of the light image. Lens 36, iris 38 and shutter 40 are mounted firmly on a mounting frame 41 at the outer edges thereof. The iris 38 and shutter 40 may be of conventional design and controlled manually or automatically in synchronism with the input signal to be displayed and recorded by utilizing a trigger signal of an oscilloscope in which the cathode ray tube 10 is used. The optical means 30 forms a well-focused image on the surface of theimage intensifier 32.

Although the detailed description is made hereinafter in both construction and operation referring to FIG. 2, the image intensifier 32 is a very thin plate member including a photoelectric converter. The image intensifier 32 intensifies the input light image and also converts the spectrum thereof into the most sensitive range of the photographic film 34a. As the light image is well focused on the photocathode surface of the image intensifier 32, the image intensifier 32 produces an intensified output light image of the same size as the input image thereto.

The photographic film in film-holding device 34 provided in contact with the output surface of the image intensifier 32 may be a Polaroid film. Any photographic film other than the Polaroid film can be used, however the Polaroid film is preferable because of high writing speed and ease of operation. The film 34a is carried within a conventional film holding device 34 and the photosensitive surface is pressed onto the output surface of the image intensifier 32 using, for example, a mechanical spring to minimize defocusing or spreading of the image.

Referring to FIG. 2, the detailed explanation of one embodiment of the present invention will be given. FIG. 2 illustrates a simplified cross-sectional view of the image intensifier 32 shown in FIG. 1. Following an image-receiving window 42 made of a thin glass plate or fiber optics, a photocathode 46 is provided. The photocathode 46 is made of, for example, sodium cesium potassium antimony (so called 5-20), cesium iodide, cesium telluride or the like. i

It is known that such materials as these emit photoelectrons when they are bombarded by a light or photon beam. Therefore, the photocathode 46 will emit photoelectrons according to the light image transmitted from an object or, in this case, from the screen 16 of the cathode ray tube through the image-receiving window 42. Facing to and equally spaced from the photocathode 46, there is provided a phosphor layer 50 on which a very thin aluminum layer 52 is provided. The phosphor material for the phosphor layer 50 may be any conventional ones, however P-ll is preferable because of its high relative photographic writing speed. The relative photographic writing speed of P-ll is twice that of P3l. However, P-3l provides the highest visual luminance of all known phosphor materials.

It is also known that different materials emit light of different wavelengths according to the energy of electrons composing the material. The photographic film 340 has a different spectrum sensitivity characteristic from a human eye. The photocathode however may be optimized in sensitivity for the objects emission spectrum. Accordingly, it is preferable to employ P-31 phosphor for the screen 16 of the cathode ray tube 10 because it emits optimum wavelengths for thevisual stimulation and P-ll phosphor for the phosphor layer 50 of the image itensifier 32 since it optimumly matches the acceptance spectrum of the photographic film thereby optimizing the writing speed.

An acceleration voltage, for example, a 7KV is applied between the photocathode 46 and the aluminum layer 52 so that a sufficient potential gradient'is formed therebetween for accelerating the photoelectrons emitted from the photocathode 50. The acceleration voltage may suitably be generated by employinga high voltage power supply 54 including a DC-DC converter driven by a battery provided within the housing 28; however, it may be applied from any external voltage source. The intensified light image derived from the light converter comprising the photocathode 46 and the phosphor layer 50 is transmitted to the photographic film 34a through a fiber optics member 56. The photocathode 46 and the phosphor layer 50 are disposed in an evacuated envelope 44.

It should be noted that the space between the photocathode 46 and the phosphor layer 50 is so small, for example, 0.10 inches and the acceleration voltage between the photocathode 46 and the aluminum layer 52 is so'high that divergence of photoelectrons emitted from the photocathode 46 is negligible without employing any electrostatic focusing means or the like. This allows the device to be simple, compact and light weight. As the image intensifier, according to the present invention intensifies the light image or the photographic writing speed by a factor of 20 or more, the beam current of the cathode ray tube 10 can be decreased for recording the'trace. The beam size of the cathode ray tube tends to increase substantially with beam current. Therefore, the resolution can be increased significantly. As is known in a TV cathode ray tube or the like, the aluminized phosphor'screen 50 ensures the increase of I the image intensity and life thereof. The aluminization also prevents problems of optical feedback from the phosphor layer 50 to the photocathode 46 which would cause sustained emissions and high background illumination.

An alternative way to form the phosphor layer 50 is to provide a light transparent conductive layer of, for example, tin oxide or the like on an input surface of the fiberoptics member 56 for operation as an anode. On an inner surface of the conductive layer, phosphor material, for example, P-ll can be deposited by the cataphorithic deposition.

The alternative method has an advantage that the phosphor layer 50 is formed uniformly by fine phosphor. particles. This increases the resolution of the photographic apparatus.

As it will be clear from the above description of one embodiment of the present invention, the photographic writing speed can be increased significantly by employ ing the image intensifier 32. Moreover, the spectrum of the output light image can be converted into the best range by selecting the phosphor material for the phosphor layer 50 regardless of the input light spectrum. The present photographic apparatus is very simple and compact in construction and less expensive. Accordingly, the photographic apparatus of the present invention is especially useful for taking pictures of dim objects or fast moving objects such, for example, as traces displayed on a cathode ray tube.

While the invention has been shown and described in a preferred embodiment, it will be understood that various modifications may be made without departing from the spirit and scope of the present invention. For example, the present photographic apparatus may be utilized for many purposes rather than for taking photographs of information displayed on a cathode ray tube. The image intensifier 32 may be a micro-channel plate with diodes, and two or more image intensifiers may be ganged together for obtaining higher gain.

What is claimed is:

shutter means for receiving, controlling, focusing,

and transmitting the light-produced information therefrom as focused light-produced information;

image intensifier means disposed adjacent said optical means and having first means for receiving said focused light-produced information and being activated thereby to produce energy-producing means and second means spaced from said first means for receiving said energy-producing means to produce an intensified image of said focused light-produced information; and

film means in engagement with said second means to record said intensified-image.

2. An apparatus according to claim 1 wherein said first means of said image intensifier means comprises photocathode means which produces said energyproducing means as photoelectrons corresponding to the focused light-produced information.

3. An apparatus according to claim 1 wherein said second means of said image intensifier means comprises phosphor means providing a spectral output which substantially matches the spectral sensitivity of said film means.

4. An apparatus according to claim 3 wherein said phosphor means has a metal layer onto which said phosphor means is disposed, means connected between said first means and said metal layer for applying an acceleration voltage therebetween to accelerate the energy-producing means from said first means.

5. An apparatus according to claim 3 wherein fiber optic light guide means are provided adjacent said phosphor means.

6. An apparatus for recording light-produced information comprising:

optical means having lens means, iris means and shutter means, said lens means focusing the lightproduced information received by said optical means to provide focused light-produced information, said iris means controlling the amount of to cused light-produced information passing through said optical means, said shutter means permitting said focused light-produced information to pass through said optical means;

image intensifier means disposed adjacent said optical means for producing an intensified image of said focused light-produced information;

film means in engagement with said image intensifier means;

first means provided by said image intensifier means for receiving said focused light-produced information and being activated thereby to produce energy-producing means; and

second means provided by said image intensifier means spaced from said first means for receiving said energy-producing means to produce said in tensified image of said focused light-produced information, said second means providing a spectral output which substantially matches the spectral sensitivity of said film means.

7. An apparatus according to claim 6 wherein cathode ray tube means having phosphor means produces the light-produced information and said first means yields optimum sensitivity to the spectral output of said phosphor means. 

1. An apparatus for recording light-produced information comprising: optical means including lens means, iris means and shutter means for receiving, controlling, focusing, and transmitting the light-produced information therefrom as focused light-produced information; image intensifier means disposed adjacent said optical means and having first means for receiving said focused light-produced information and being activated thereby to produce energyproducing means and second means spaced from said first means for receiving said energy-producing means to produce an intensified image of said focused light-produced information; and film means in engagement with said second means to record said intensified image.
 2. An apparatus according to claim 1 wherein said first means of said image intensifier means comprises photocathode means which produces said energy-producing means as photoelectrons corresponding to the focused light-produced information.
 3. An apparatus according to claim 1 wherein said second means of said image intensifier means comprises phosphor means providing a spectral output which substantially matches the spectral sensitivity of said film means.
 4. An apparatus according to claim 3 wherein said phosphor mEans has a metal layer onto which said phosphor means is disposed, means connected between said first means and said metal layer for applying an acceleration voltage therebetween to accelerate the energy-producing means from said first means.
 5. An apparatus according to claim 3 wherein fiber optic light guide means are provided adjacent said phosphor means.
 6. An apparatus for recording light-produced information comprising: optical means having lens means, iris means and shutter means, said lens means focusing the light-produced information received by said optical means to provide focused light-produced information, said iris means controlling the amount of focused light-produced information passing through said optical means, said shutter means permitting said focused light-produced information to pass through said optical means; image intensifier means disposed adjacent said optical means for producing an intensified image of said focused light-produced information; film means in engagement with said image intensifier means; first means provided by said image intensifier means for receiving said focused light-produced information and being activated thereby to produce energy-producing means; and second means provided by said image intensifier means spaced from said first means for receiving said energy-producing means to produce said intensified image of said focused light-produced information, said second means providing a spectral output which substantially matches the spectral sensitivity of said film means.
 7. An apparatus according to claim 6 wherein cathode ray tube means having phosphor means produces the light-produced information and said first means yields optimum sensitivity to the spectral output of said phosphor means. 